[Feature] Add AllGather-KV sequence-parallel attention str… (#4968)

Signed-off-by: zhuhh97 <zhuhonghan@huawei.com>
Signed-off-by: dph97 <nenbaying@163.com>
Signed-off-by: zhuhh97 <zhh@unknown>
Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>
Co-authored-by: dengyunyang <584797741@qq.com>

vllm_omni/entrypoints/cli/serve.py

@@ -473,6 +473,14 @@ class OmniServeCommand(CLISubcommand):
             help="Ring Sequence Parallelism degree for diffusion models. "
             "Equivalent to setting DiffusionParallelConfig.ring_degree.",
         )
+        omni_config_group.add_argument(
+            "--allgather-degree",
+            dest="allgather_degree",
+            type=int,
+            default=None,
+            help="AllGather-KV Sequence Parallelism degree for non-causal diffusion attention. "
+            "Equivalent to setting DiffusionParallelConfig.allgather_degree.",
+        )
         omni_config_group.add_argument(
             "--diffusion-quantization-config",
             type=json.loads,